1. Field of the Invention
The present disclosure relates to a novel artificial SEI cathode material for use in a rechargeable lithium-ion battery. Accordingly, the present disclosure also relates to a lithium-ion battery comprising a cathode formed from the afore-mentioned novel artificial SEI cathode material.
2. Description of Related Art
Lithium-ion secondary battery includes a cathode and an anode including materials in which lithium intercalation/de-intercalation reversibly occurs as the cathode and anode active materials, and an organic electrolyte present between the cathode and anode electrodes. The batteries produce and store electric energy by a redox reaction when the lithium ions are intercalated into and de-intercalated from the cathode electrode and the anode electrode.
The performance of cathode material in the conventional lithium-ion battery is often limited by irreversible capacity loss (ICL) in the first cycle caused by solvent decomposition on the cathode surface, as well as the irreversible insertion of lithium ion into the cathode layer that lead to the formation of a passive film (i.e., a solid electrolyte interface (SEI) layer) on the cathode surface. The ICL also manifested in high impedance values observed in the beginning of the first charge and discharge cycle of the lithium battery, however, such phenomenon is often discarded by the skilled artisan in this field on the assumption that the electrodes are blocked by the formation of SEI film that resulted in high internal resistance on the cathode surface or by attributing it to be part of the charge-transfer resistance. The commercial available coin cell type lithium-ion battery typically claims an equivalent series resistance (ESR) value in the range of 30-200 ohms, with the majority being above 75 ohms. The high resistance translates to large ohmic losses in the capacity of the battery during the charge and discharge phases, such losses further adversely affects the battery by interfering with the its ability to be efficiently charged and/or discharged in a short period of time. Thus, it is reasonable to conclude that the normal operation of a lithium battery is closely connected to the stability and conductivity of SEI film.
Accordingly, there exists in the art a need for an improved cathode material, in which a relatively stable and conductive SEI film may be formed on at least part of the surface of the cathode material, so that when the cathode formed from the improved artificial cathode material of the present disclosure is incorporated into a rechargeable lithium battery, improved electrochemical properties such as a low ESR, an enhanced capacitance, and a long cycle lifetime are rendered to the rechargeable lithium battery.